The invention relates to a low-voltage circuit breaker having poles containing levers for opening and closing the contacts, with terminals protruding from the circuit breaker and an electric arc extinction chamber.
It is known that in low-voltage circuit breakers, for example those for rated currents up to 6000 A, large electrodynamic and thermal stresses occur in the event of faults or short-circuits. The supporting structure of these circuit breakers must therefore be very robust and stiff and is usually made from metallic material. Moreover, it is known that electrical insulation devices are present in the circuit breaker in order to insulate the various phases or poles from one another and to insulate the live parts (or parts carrying current) from the metallic structure.
At the present time these electrical insulation devices consist of a complex series of protections or insulating barriers interposed between the live components (levers and terminals) and the supporting structure and between the live components of different phases. The supporting structures of the circuit breakers are made so as to receive several phases or poles and the control device for opening and closing the circuit breaker.
The dimensioning of the insulating protections has to take into consideration both the nominal working conditions and also the working conditions after many years of operation (with the circuit breaker soiled or fouled) and conditions which occur during a fault or short-circuit of the electrical line. However, the safety and electrical insulation characteristics provided for by the standards relating to personnel working near the circuit breaker and relating to the system in which the circuit breaker is connected must be guaranteed to be unimpaired for all conditions of operation of the circuit breaker.
The present-day make-up of circuit breakers demands very rigid phases of assembly. This poor flexibility in production is brought about essentially by the fact that in the structure of the circuit breaker there are insulating bases for supporting the live parts made as structural monoblocs which cannot be subdivided in the production process into preassembled subgroups or more generally into homogeneous families of components which permit flexibility and rationality in the production phases.
It is not therefore possible to customize the circuit breaker only in the final phases of the production chain, rather it is necessary to provide different production lines for each model of circuit breaker. This poor flexibility in production demands large investments in space for the assembly lines, heavy employment of resources and a consequent low level of productivity.